1. Field of the Invention
The present invention relates to apparatus and methods for unloading plastic bottles and/or jars or containers, stored in stacks of tiers on a movable pallet.
2. Prior Art
Glass bottles and/or jars, or glass containers, have long been used in commercial packaging for merchandise of all kind. Plastic bottles and/or jars, or plastic containers, more recently serve substantially the same purpose as corresponding glass containers and appear to be preferred over glass containers in the commercial market. Plastic containers are less expensive to manufacture than corresponding glass containers. Plastic containers are less fragile than corresponding glass containers although most glass containers are more scratch resistant than most plastic containers. Plastic however, weighs substantially less than corresponding glass, making plastic containers lighter in weight than corresponding glass containers.
Plastic containers are usually manufactured in large volume and are stored in hoppers, bins or stacks of tiers. When plastic containers are stored in stacks of tiers, the stack of tiers of plastic containers is usually supported on a pallet, making the stack of tiers of plastic containers conveniently movable, using a fork-lift apparatus, for example.
A stack of tiers of plastic containers usually consists of a support means such as a support sheet or tier sheet, on which a quantity of plastic containers are aligned, utilizing the upper surface of the support sheet or tier sheet. Depending on the size of the plastic container, a tier of plastic containers may include as many as 200 to 300 plastic containers. Each tier, in a stack of tiers, may include a support sheet or tier sheet supporting or retaining a plurality of plastic containers, aligned on the support sheet. There may be as few as eight (8) tiers and as many as twenty (20) tiers, in a stack of tiers, depending on the size, in the height, of the container and the height of the stack. The stacking or cascading of a relatively large number of tiers, one on top of the other, on a pallet, makes a relatively unstable stack. However, a pallet and the stack of tiers of plastic containers held on the pallet are potentially highly movable and conveniently storable. In order to provide a more stable load on a pallet, the stack of tiers may be secured to the pallet by straps or bands. The straps may extend longitudinally about and over the stack of tiers and secure the stack of tiers of plastic containers to the pallet. The straps used to secure the stack of tiers to the pallet may be secured to or extended about the pallet supporting the stack of tiers. The use of straps or bands for securing a stack of tiers to a pallet may require a cover or support sheet covering the top tier in the stack of tiers. With the stack of tiers secured to the supporting pallet, the stack of tiers is more stable and may be more easily moved horizontally or vertically. Another stack stabilizing process is to cover the stack with a sheet, such as a plastic sheet, for example. A sheeting cover will stabilize the load on the pallet and also cover the stack, keeping the contents clean.
Empty plastic containers having essentially identical physical characteristics are usually stored in mass, such as in bins or in hoppers, or in stacks of tiers on a platform or pallet, for example. Stacks of tiers of plastic containers are easily and readably stored and easily moved. However, the containers in the stack of tiers of plastic containers must be unloaded from the stack in order to use the containers. Examples of pallet unloading apparatus teachings are found in the United States patents:
U.S. Pat. No. 4,231,697 ('697) to Franz issued Nov. 4, 1980; PA1 U.S. Pat. No. 4,493,599 ('599) to Hartness, et al issued Jan. 15, 1985; PA1 U.S. Pat. No. 5,033,929 ('929) to Marti issued Jul. 23, 1991.
The Franz '697 patent teaches apparatus for removing each of a plurality of aligned plastic containers from a conveyor and positioning the containers in aligned rows on a platform in a stacked tier arrangement. Movable arms controllably secure each tier of containers and controllably remove the tier of containers from the stack of tiers. The apparatus taught in the '697 patent moves containers by pushing the containers with movable arms. Containers having medium to large size base may be easily moved but moving containers with small base in the manner taught by this patent is not practical because small base container is much more subject to being tipped over and one fallen container in a tier of containers may jeopardize movement of an entire tier of containers.
The Hartness et al '599 patent teaches apparatus for depalletizing tiers of articles, such as bottles or containers, for example, from a multi-tier stack of tiers carried on a pallet. The walls or sections of a four-wall clamp surround the containers forming the top tier of the multi-tier stack. The walls of the clamp move inwardly, applying pressure to the outer containers in the tier of containers, pressing the containers together, so as to clamp or grip the containers defining the top tier. The top tier of containers is pressure secured and removed from the stack of tiers The integrity of the apparatus taught in the '599 patent depends on the efficiency of the pressure applied to the tier of containers. Should the pressure been too great, the containers will be crushed and the entire tier will be lost. Should the pressure be too little, the containers will not hold together and the entire tier will be lost. Further, the apparatus in the '599 teaching includes an elevator means that both elevates and lowers the containers handled by the apparatus. After the top tier is removed, the next tier in the stack of tiers is singularly elevated into a top tier position. The top tier is removed from the stack, cleared from the stack and lowered to a receiving table.
The Marti '929 patent teaches apparatus for unloading trays of bottles or containers stacked on a pallet. The stack of trays is positioned on an elevator means which elevates the stack of trays incrementally, so that the top tray of the stack is raised into a work position. A device having a gripper arrangement secures the top tray in the stack. The top tray is gripped by the gripper means and inverted, dumping the contents of the top tray into a hopper. The apparatus in the Marti '929 teaching requires that the contents of each tier be arranged in trays or at least on a tier sheet with some vertical siding or walling defining the ends of the support sheet. Without supporting the containers in trays or on a sheet with walls or vertical extended siding defining the edge of the support sheet, a tier of containers could not be handled as Marti '929 teaches.